I don't think this has anything to do with autism, ADHD, or neurodivergence.
Intelligent people are curious. That's what makes them intelligent.
IMHO neurodivergent people don't have a trait for "curiousity" -- they're just more intelligent (if their neurodivergence isn't too severe) and so are interested in things. That's why there's so many in technical and engineering fields, mathematics, science -- the really hard stuff (hard for most people.)
Yeah, it's still not easy because there's so much other stuff going on inside the mind, but all that other stuff is going to lead to some pretty cool thoughts that could turn into a paper, project, business, thesis, etc. (if you manage to remember them long enough to write them down!) Over years this builds brain matter and this is where the intelligence comes from (again assuming the neurodivergence isn't severe.)
By "intelligence" I mean the raw ability to process information and gain understanding from it. Not IQ.
There's a difference between "I'm very curious" and "I literally can't move my attention from this thing, even if I want to, to the point that I will forget to eat or sleep or bathe"
The way I understand it (based on some introspection and reading the experiences of other autistic people), it's not a matter of ability to process information but rather the inability to not process information. We don't have the innate ability to recognize what's important and what isn't, which hinders our ability to recognize that two situations are the same and should be handled the same way. Asking "why?" is an attempt at understanding the pattern so that we can generalize in the same way as other non-autistics instead of memorizing every individual situation.